1. Field of the Invention
The present invention relates to the reduction of noise of a rotary part of an enclosed compressor of a two cylinder type as well as the improved accuracy in assembling the same compressor.
2. Description of the Prior Art
FIGS. 9A and 9B respectively show section views of a conventional compressor of a two cylinder type, which is disclosed in, for example, Japanese Utility Model Publication (Kokai) Sho-48-10515. In FIGS. 9A and 9B, reference character 1 designates a closed vessel; 2, a motor element; 3, a stator mounted to the closed vessel 1 in a shrinkage fit manner; 4, a rotor which cooperates with the stator 3 in forming the motor element 2; 4a, an axial hole formed in the rotor 4; 5, a first rotary shaft which is press fixed to the rotor 4; 6, a first compression element to be driven by the first rotary shaft 5; 7, a second rotary shaft; 7a, an eccentric portion of the second rotary shaft 7; 8, a key which is used to restrict the sliding of the second rotary shaft 7 and rotor 4; 9, a key storage groove formed in the rotor 4; 10, an air gap formed between the rotor 4 and stator 3; and 11, a fastening clearance which is set smaller than the air gap 10 and is formed between the second rotary shaft 7 and rotor 4. Also, 12 stands for a second compression element which is composed of a cylinder 13, a rolling piston 14 and the above-mentioned rotary shaft 7. Further, 15 designates a first main bearing which is used to support the first rotary shaft 5; 16, a second main bearing used to support the second rotary shaft 7; 18, a second sub bearing for supporting the second rotary shaft 7; and 19, an opening which is formed by the end portion of the second rotary shaft 7 and a second sub bearing 18 and is closed by an end plate 20. In addition, the first compression element 6 is similar in structure to the second compression element 12, 26 designates a suction pipe, and 27 stands for a discharge pipe which discharges compressed gas.
Next, description will be given below of the operation of the above-mentioned conventional compressor. If the stator 3 and rotor 4 cooperating together to form the motor element are electrically energized, then the rotor 4 is allowed to start rotating, which drives the first rotary shaft 5 to rotate and also drives through the key 8 the second rotary shaft 7 to rotate. In the second compression element 12, the rolling piston 14 mounted to the eccentric portion 7a of the second rotary shaft 7 is caused to rotate eccentrically to thereby compress gas sucked in through the inlet pipe 26, and the compressed gas is then discharged through the discharge pipe 27 mounted to the closed vessel 1. Also, in the first compression element 6, a similar operation is executed.
However, since the conventional two cylinder type compressor is constructed in the above-mentioned manner, the movement of the second rotary shaft in the axial direction thereof is made unstable, with the result that noise is easy to occur due to the unstable axial movement of the second rotary shaft. Also, due to the fact that the second rotary shaft 7 is fastened to the rotor 4 by the key 8, noise is easy to occur due to a backlash between them. Further, because the inner periphery of the rotor 4 is repeatedly contacted with and removed from the second rotary shaft 5, there is generated noise.
Also, due to the fact that the first and second rotary shafts 5 and 7 are constructed in an integral structure by the rotor 4, especially, in assembling the compressor, there is required a high assembling accuracy in paralleling and aligning axially the first and second main bearings 15 and 16 with each other and, if such high accuracy cannot be secured, then the performance and reliability of the compressor are lowered and noise is increased, which are problems to be solved.